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A relativistic plane wave formalism for quasifree eta meson photoproduction is presented. The sensitivity of the unpolarized differential cross section, the recoil nucleon polarization, and the photon asymmetry is investigated. The results indicate that the S₁₁ resonance dominates the unpolarized differential cross section, but that its contribution to the spin observables are very small, for which the D₁₃ resonance plays the primary role.

Polarization observables of the three charge states of the pion for the γd→πNN reaction with polarized photon beam and/or oriented deuteron target are evaluated over the whole Δ(1232)-resonance region adopting a nonrelativistic model based on time-ordered perturbation theory. Results for the π-meson spectra, linear photon asymmetry, vector and tensor target asymmetries are presented. Particular attention is given, for the first time, to double polarization asymmetries for which we present results for and . We find that all other double polarization asymmetries of photon and deuteron targets vanish.

The helicity-dependent coherent π⁰-photoproduction in the reaction γd → π⁰d near the η-threshold is investigated. The calculations are performed within an approach which includes the reaction amplitudes of the impulse approximation (IA), two-step process with intermediate πN- and ηN-rescattering, and the higher order terms in the multiple scattering series for the intermediate ηNN interaction. The contribution of γd → π⁰d to the deuteron spin asymmetry is calculated and its contribution to the Gerasimov–Drell–Hearn (GDH) integral is explicitly evaluated by integration up to a photon energy of 900 MeV. In addition, the helicity E-asymmetry is calculated. The results revealed that the doubly polarized differential cross-sections and the helicity E-asymmetry are sensitive to the interference of rescattering effects, specially at photon energies 600–800 MeV and extreme backward pion angles. The sensitivity of the obtained results for the GDH integral to the choice of NN potential model governing the deuteron wave function is discussed. We find that the deviation among results obtained for the deuteron GDH integral using different deuteron wave functions is quite large.

Tensor target spin asymmetries $T_{2M}$ ($M$=0,1,2) in the reaction $\gamma d\to {\pi }^{-}pp$ are studied for photon energies from $\pi$-threshold up to 1.5GeV with inclusion of rescattering effects. It is shown that the influence of rescattering effects on the tensor target spin asymmetries is sizable in the energy region near $\pi$-threshold. At higher energies, much smaller influence of rescattering effects is seen. The sensitivity of the obtained results to the elementary pion photoproduction operator is investigated and a considerable dependence is found, in particular at forward pion angles. In addition, a comparison with results of other theoretical models is also given. The extracted spin asymmetries are compared with available experimental data and a qualitative agreement is obtained. The predictions presented here may be useful to interpret the recent measurements from the VEPP-3 electron storage ring.

A component of the total cross section of the deuteron-deuteron interaction connected with the vector polarized ($P_y$) one initial deuteron and tensor polarized ($P_{xz}$) another one constitutes a null-test signal of the T-invariance violation but P-parity conservation. The energy dependence of this signal is calculated here at beam kinetic energies per nucleon of 0.1–1GeV within the Glauber spin-dependent theory of multiple scattering in the S-wave approximation for the deuteron wave function.

In a recent paper [A. Ahanj et al., Phys. Lett. A368 (2007) 34], we gave a classical protocol to simulate quantum correlations corresponding to the spin-s singlet state for the infinite sequence of spins satisfying 2s + 1 = 2ⁿ. In the present paper, we have generalized this result by giving a classical protocols to exactly simulate quantum correlations implied by the spin-s singlet state corresponding to all integer as well as half-integer spin values s. The class of measurements we consider here are only those corresponding to spin observables, as has been done in the above-mentioned paper. The required amount of communication is found to be ⌈log₂(s + 1)⌉ in the worst case scenario, where ⌈x⌉ is the least integer greater than or equal to x.

A scheme based on the chiral Lagrangian, analyticity and unitarity is applied to spin observables in pion photoproduction and nucleon Compton scattering. Subthreshold partial-wave amplitudes are calculated in chiral perturbation theory and extrapolated beyond the threshold region imposing the micro-causality and the unitarity constraint. A reasonable description of various spin observables up to energies $\sqrt{s}\simeq 1300$ MeV is obtained in terms of the parameters relevant at order $Q^3$ in the chiral Lagrangian. Nucleon spin-polarizabilities predicted in our scheme are consistent with recent measurements of double polarization asymmetries at MAMI.